Many industrial machines (e.g., wind turbines, locomotives, trucks, earth-moving equipment, and the like) include assets or assemblies (e.g., mechanical drive trains, engines, gearboxes, and the like) that operate within difficult environments and/or endure substantial amounts of thermal or torsional stress as well as shock and vibration. It is often desirable to monitor a condition of an element or assembly so that it may be replaced or repaired before severe and permanent damage is sustained by the machine. Often, fluid lubricants are used to provide lubrication and cooling to increase performance of the machine and/or to increase the operational lifetime of the machine. Lubricants reduce the friction between two parts that engage each other and may also dissipate heat that is generated by the friction between the two parts. In addition to lubricants, machines may use other industrial fluid such as fuels, hydraulic media, drive fluids, power steering fluids, power brake fluids, drilling fluids, oils, insulating fluids, heat transfer fluids, or the like. Such fluids allow efficient and safe operation of machinery in transportation, industrial, locomotive, marine, automotive, construction, medical, and other applications.
The quality of a lubricant may decrease over time due to the introduction of contaminants and/or aging of the lubricant. Lubricants in a reservoir can become contaminated by contaminants such as water, metallic particles, and non-metallic particles. Contaminated fluids may lead to damaged parts or a decreased performance of the machine. Water is a common and destructive lubricant contaminant. The water may be introduced from a coolant leak, condensation from environmental exposure, equipment cleaning, and/or combustion. Water adversely affects the lubricant properties by increasing engine wear, causing corrosion of the reservoir, and/or accelerating oxidation of the lubricating fluid, such as oil. In addition, the repetitive thermal and viscous cycles in normal operation conditions may cause the lubricating fluid to age and chemically break down, which results in a reduction in lubricating performance of the fluid, such as an increased viscosity. Furthermore, stabilizing additives that are added to the lubricants to provide increased resilience within harsh environments, such as high temperatures, may begin to break down over time as well. The reduction in additive concentration provides less thermal stability for the lubricant, causing the lubricant to degrade at a faster rate. As the additive is depleted, acidic components, such as by-products from the degradation of the additive and/or the lubricant due to aging, may be introduced into the lubricant fluid. The acidic components, like water, are polar contaminants that reduce the effectiveness and performance of the lubricant.
Conventional methods of inspecting fluids of a machine include visual inspection of the fluid (e.g., dipsticks) or a sensor that is directly wired to a system. These methods may not be practical and/or may have limited capabilities. For example, due to the configuration of some machines, it may be difficult to visually inspect the fluid. Also, hardwired sensors may not be suitable for machines that frequently move and/or are exposed to harsh conditions.
Robust sensing of fluids may be useful in mobile and stationary equipment applications. As an example, if the equipment is a vehicle engine and the fluid is engine oil, then knowledge about oil health may be used to help reduce or prevent unexpected downtime, provide savings from unnecessary oil replacement, extend the operating lifetime of the oil and/or the asset (e.g., gearbox, engine, etc.) in which the oil is disposed, and improve service intervals scheduling.
Standard (classic) impedance spectroscopy is a technique that is employed to characterize aspects of material performance. In classic impedance spectroscopy, a material may be positioned between electrodes and probed over a wide frequency range (from a fraction of Hz to tens of GHz) to extract the fundamental information about dielectric properties of the material. Standard impedance spectroscopy may be limited due to its low sensitivity in reported measurement configurations and prohibitively long acquisition times over the broad frequency range. Therefore, standard impedance spectroscopy is difficult to perform in the field.
It may be desirable to have systems and methods for in-situ monitoring of fluid properties that differ from those systems and methods that are currently available.